(a) Field of the Invention
The present invention relates to a liquid crystal display and, more particularly, to a liquid crystal display which bears wide viewing angle.
(b) Description of the Related Art
Generally, a liquid crystal display has two substrates with a plurality of electrodes, a liquid crystal layer sandwiched between the two substrates, and two polarizing plates externally attached to the substrates. Voltages are applied to the electrodes so that the liquid crystal molecules in the liquid crystal layer are re-oriented to thereby control the light transmission.
One of the substrates is formed with thin film transistors for switching the voltages applied to the electrodes, and a plurality of gate and data lines proceeding in the row and column directions. The data lines cross over the gate lines while defining pixel regions. A pixel electrode is formed at each pixel region. The thin film transistors receive scanning signals from the gate lines, and picture signals from the data lines. The thin film transistors control the picture signals pursuant to the scanning signals, and transmit the controlled picture signals to the pixel electrodes. The other substrate is formed with color filters corresponding to the pixel electrodes, and a common electrode at its entire surface.
In a vertically aligned (VA) mode liquid crystal display, the long axes of the liquid crystal molecules are arranged vertical to the substrates without application of an electric field, and under the application of voltages, inclined such that they are disposed to be parallel to the substrates. The liquid crystal molecules where the long axes thereof are oriented vertical to the substrates cannot rotate the polarizing direction of the light, whereas the liquid crystal molecules where the long axes thereof are oriented parallel to the substrates can rotate the polarizing direction of the light, assuming that the polarizing axes of the polarizing plates are arranged vertical to each other. When the liquid crystal molecules are oriented vertical to the substrates, the light does not pass the polarizing plates so that the display screen becomes to be in a dark state. When the liquid crystal molecules are inclined under the application of voltages, a predetermined amount of light passes the polarizing plates so that the display screen becomes to be in a bright state.
In such a VA mode liquid crystal display, it has been proposed that opening patterns or organic material-based protrusions might be formed at the electrodes while forming multiple pixel domains. With the formation of the multiple pixel domains, the liquid crystal molecules are uniformly inclined in four directions, thereby obtaining wide viewing angle.
Meanwhile, such a protrusion may be used as a spacer. The height of the protrusion suitable for the domain partitioning may be established to be about 1.2 xcexcm, but that suitable for the spacer use should be established to be about 4.0 xcexcm. Accordingly, in order to directly use the domain partitioning protrusion as the spacer, the height of the protrusion would be established to be about 4.0 xcexcm. However, in this case, it becomes difficult to inject the liquid crystal material in-between the substrates due to the barrier of the protrusion.
It is an object of the present invention to provide a liquid crystal display with protrusion patterns which can make the desired domain partitioning while being used for the spacer purpose.
It is another object of the present invention to provide a liquid crystal display which bears enhanced brightness.
These and other objects may be achieved by a liquid crystal display where protrusion patterns are formed to be used as a spacer while making the desired domain partitioning.
According to one aspect of the present invention, the liquid crystal display includes a first insulating substrate, and pixel electrodes formed on the first insulating substrate each with a plurality of opening patterns. The pixel electrode is partitioned into a plurality of micro-regions by way of the opening patterns. A second insulating substrate faces the first insulating substrate. A common electrode is formed on the second insulating substrate. A liquid crystal layer is sandwiched between the first and the second insulating substrates. A plurality of protrusion patterns are formed on the common electrode. The protrusion patterns are placed at the micro-regions of the pixel electrode to regulate the inclining directions of liquid crystal molecules in the liquid crystal layer. The gap between the first and the second substrates is constantly maintained by way of the protrusion patterns.
A thin film transistor is formed on the first insulating substrate while being electrically connected to the pixel electrode. A black matrix is interposed between the second insulating substrate and the common electrode while being patterned. Color filters are interposed between the second insulating substrate and the common electrode corresponding to the pixel electrodes.
The protrusion pattern is shaped with a pillar where the top and the bottom sides thereof have a shape of a circle, a rectangle, or a rectangle with curved edges. The protrusion pattern has a height of 3.0-4.5 xcexcm.
The retardation value of the liquid crystal layer is in the range of 0.25-0.4 xcexcm.
The light incident upon the liquid crystal layer is circularly polarized. First and second polarizing plates are externally attached to the first and the second substrates, and first and second bi-axial films are interposed between the first substrate and the first polarizing plate and between the second substrate and the second polarizing plate, respectively.
A mono-axial film may be interposed either between the first polarizing plate and the first bi-axial film, or between the second polarizing plate and the second bi-axial film.
The longest axis of the first bi-axial film is perpendicular to the longest axis of the second bi-axial film. The polarizing axes of the first and the second polarizing plates are angled with respect to the longest axes of the first and the second bi-axial films by 45xc2x0.
First and second xcex/4 plates are interposed between the first substrate and the first bi-axial film and between the second substrate and the second bi-axial film, respectively. The slow axes of the first and the second xcex/4 plates are perpendicular to each other. The polarizing axes of the first and the second polarizing plates are angled with respect to the slow axes of the first and the second xcex/4 plates by 45xc2x0.
The polarizing axis of the first polarizing plate is parallel to the longest axis of the first bi-axial film, and the polarizing axis of the second polarizing plate is parallel to the longest axis of the second bi-axial film.
According to another aspect of the present invention, the liquid crystal display includes a first insulating substrate, and pixel electrodes formed on the first insulating substrate each with opening patterns. A second insulating substrate faces the first insulating substrate. A common electrode is formed on the second insulating substrate. First and second protrusions are formed on the common electrode. The first protrusion has a first thickness, and the second protrusion has a second thickness larger than the first thickness. A liquid crystal layer is sandwiched between the first and the second substrates.
A thin film transistor is formed on the first insulating substrate while being electrically connected to the pixel electrode. A black matrix is interposed between the second substrate and the common electrode while being patterned. Color filters are interposed between the second substrate and the common electrode corresponding to the pixel electrodes.
The first and the second protrusions may be based on a photosensitive organic insulating film, a photoresist film, or a silicon-containing insulating film. The first protrusion has a width of 3-15 xcexcm.
The second protrusion is pillar-shaped with top and the bottom sides having a shape of a polygon or a circle. The top and the bottom sides of the second protrusion have a width of 5-40 xcexcm.